Continuous-wave irradiation

Output from both gated continuous wave and pulsed carbon dioxide lasers has been used to desorb ions from surfaces and then to photodissociate them in a Fourier transform ion cyclotron resonance mass spectrometer. Pulsed C02 laser irradiation was most successful in laser desorption experiments, while a gated continuous wave laser was used for a majority of the successful infrared multiphoton dissociation studies. Fragmentation of ions with m/z values in the range of 400-1500 daltons was induced by infrared multiphoton dissociation. Such photodissociation was successfully coupled with laser desorption for several different classes of compounds. Either two sequential pulses from a pulsed carbon dioxide laser (one for desorption and one for dissociation), or one desorption pulse followed by gated continuous wave irradiation to bring about dissociation was used. 

In Chapter 5 we observed NOE interactions by ID NOE difference, measuring the steady-state NOE resulting from a long (several seconds), low-power continuous-wave irradiation of one nucleus. The modern selective (DPFGSE) ID NOE experiment... 

This result is also correct for continuous-wave irradiation where the effective spin-lock field is Wrf = o)rf leading to the same result as in Equation (4.51). 

Figure 3. The effect of fluence rate and light fractionation on BPD-mediated PDT. BPD-MA was administered to rats with NBT II tumors implanted into the bladder wall. One hour later tumors were exposed to a total fluence of 30 J/cm of 690 nm irradiation under the following conditions 100 mWcm"- continuous 100 mW/cm - fractionated 15 s on/15 s off 100 mWcm 2 30 s on/30 s off 100 mWcm" 60 s on/60 s off. Tumors were disaggregated 24 h later and tumor cells were plated for colony formation assay. Colonies (50 cells or more) were counted 9 days later after fixing with methanol and staining with crystal violet. The Wilcoxon rank sum test was used to compare the number of clonogenic cells with data at 100 mWcm - and continuous wave irradiations. NS not significant. (Source linuma et al. [32]. Reproduced with permission.)...

Cimrova V, et al. 2002. Comparison of the birefringence in an azobenzene side chain copolymer induced by pulsed and continuous wave irradiation. Appl Phys Lett 81(7) 1228 1230. 

New impetus was given to photomedicine by development of lasers that are compatible with the clinical environment. These include HeNe, Ar ion, mby, and tunable dye lasers operating in the continuous wave (cw) mode. Prior to the advent of lasers in medicine, only the treatment of newborn jaundice, and the appHcation of long wavelength uv irradiation in conjunction with adininistration (or topical appHcation) of psoralen class sensitizers to treatment of skin diseases (86), principally psoriasis, were clinically important phototherapies. 

Depending on how the secondary magnetic field is applied, there are two fundamentally different types of spectrometers, namely, continuous wave (CW) and pulse Fourier transform (PFT) spectrometers. The older continuous wave NMR spectrometers (the equivalent of dispersive spectrometry) were operated in one of two modes (i) fixed magnetic field strength and frequency (vi) sweeping of Bi irradiation or (ii) fixed irradiation frequency and variable field strength. In this way, when the resonance condition is reached for a particular type of nuclei (vi = vo), the energy is absorbed and... 

By employing a laser for the photoionization (not to be confused with laser desorption/ ionization, where a laser is irradiating a surface, see Section 2.1.21) both sensitivity and selectivity are considerably enhanced. In 1970 the first mass spectrometric analysis of laser photoionized molecular species, namely H2, was performed [54]. Two years later selective two-step photoionization was used to ionize mbidium [55]. Multiphoton ionization mass spectrometry (MPI-MS) was demonstrated in the late 1970s [56—58]. The combination of tunable lasers and MS into a multidimensional analysis tool proved to be a very useful way to investigate excitation and dissociation processes, as well as to obtain mass spectrometric data [59-62]. Because of the pulsed nature of most MPI sources TOF analyzers are preferred, but in combination with continuous wave lasers quadrupole analyzers have been utilized [63]. MPI is performed on species already in the gas phase. The analyte delivery system depends on the application and can be, for example, a GC interface, thermal evaporation from a surface, secondary neutrals from a particle impact event (see Section 2.1.18), or molecular beams that are introduced through a spray interface. There is a multitude of different source geometries. 

UFPs of the Fe-N system can be synthesized from iron pentacarbonyl Fe(CO)s] and NH3 as reactants by a IOOO-W continuous wave C02 laser irradiation. The NH, gas is the absorbent of the laser beam in this case. At the lower synthesis temperature, below 650°C, UFPs of y -Fe4N with particle size of 10-25 nm grew dominantly. Above 1150°C, however, the growth of y-Fe UFPs with larger particle size of 30-100 nm was predominant (73). Iron carbonitride (lCN) UFPs were also synthesized from the ternary reactants of Fe(CO)s, NH3, and C2H i. The structure oflCN UFPs was hexagonal with e-Fe3(N,C) phase. A large saturation magnetization up to 142 emu/g was obtained and was ascribed to the carbon layer on 1CN UFPs (74). 

Under UV-laser irradiation, photosensitive multifunctional acrylate resins become rapidly cross-linked and completely insoluble. The extent of the reaction was followed continuously by both UV and IR spectroscopy in order to evaluate the rate and quantum yield of the laser-induced polymerization of these photoresist systems. Two basic types of lasers emitting in the UV range were employed, either a continuous wave (C.W.) argon-ion laser, or a pulsed nitrogen laser. 

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